Hickory

• 1. Introduction

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  Hickory trees belong to the genus Carya, and they have been part of North American landscapes since before humans arrived on the continent. The oldest fossils tied to this genus are Cretaceous pollen grains found in Mexico and New Mexico. What tree produces nuts so nutritious that dried kernels are 64% fat and deliver more than twice the daily requirement of manganese in a single hundred-gram serving? What wood is so uniquely tough that engineers and craftspeople have never found another commercial species that matches its combination of strength, hardness, stiffness, and shock resistance all at once? And what is the story of a genus that once stretched across the entire Northern Hemisphere, only to be erased from Europe by ice and nearly squeezed out of North America by the same forces? Those are the questions this documentary sets out to answer.

• 2. A Name from the Woodlands

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  The word "hickory" came into English from a Native American language in the Algonquian family, possibly Powhatan. It is a shortening of words recorded as pockerchicory or pocohicora, and the original term may have referred either to the nut of the tree or to a milky drink made from those nuts. The genus name Carya takes a different path entirely: it comes from the ancient Greek word káryon, meaning simply "nut."

  Indigenous peoples of the Eastern Woodlands of North America had relied on hickory nuts as a significant food source since the middle Archaic period. The Cherokee, for instance, used them in a dish called Kanuchi soup, and more commonly extracted edible oil by crushing the nuts and then straining or boiling the remains. The bark offered its own uses: the Cherokee produced a green dye from hickory bark for coloring cloth, and when they mixed that bark with maple bark, the result shifted to a yellow pigment. Burnt hickory wood left behind ash that could be processed into a strong lye suitable for making soap.

• 3. Deep Time and Shifting Ice

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  Modern Carya first appeared in Oligocene strata laid down 34 million years ago. Fossil and molecular data together suggest the genus may have diversified during the Miocene, and recent discoveries of Carya fruit fossils have strengthened the picture of a genus long embedded in Eastern North American terrain.

  Fossils of early hickory nuts show simpler, thinner shells than those found on most living species. The exception is the pecan, which retains a notably thin shell. The working hypothesis is that the trees gradually thickened their shells over time as a defense against rodent seed predation. During the period when those shell changes were happening, Carya ranged across the Northern Hemisphere. The Pleistocene Ice Age, beginning around 2 million years ago, erased the genus from Europe entirely. In Anatolia, the genus appears to have survived longer, disappearing only in the early Holocene, probably because of human disturbance rather than climate. Carya also withdrew from everything west of the Rocky Mountains in North America, and it has not returned. Scientists believe the genus originated in North America and later spread to Europe and Asia, meaning the continents that lost it were not its original home.

• 4. Nineteen Species, Two Continents

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  Plants of the World Online currently accepts 19 species within Carya. Twelve are native to North America, and seven are native to Southeast Asia, distributed across China, Indochina, and the Assam region of northeastern India. Of the North American twelve, eleven occur in the United States, four are found in Mexico (including one, Carya palmeri, that grows nowhere else), and five extend into southern Canada.

  Within the Asian group, one species stands apart botanically. Carya sinensis, sometimes called beaked hickory, is the only evergreen member of a genus that is otherwise deciduous. Genetic data place it firmly within the Asian Carya rather than as a separate genus, which is why Plants of the World Online does not recognize the older name Annamocarya sinensis, despite it having been used in the past. The genus also hybridizes readily; around nine named hybrids are accepted, a sign of how genetically compatible the species within Carya remain despite their wide geographic spread.

• 5. How a Hickory Grows

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  Hickory flowers are small, yellow-green catkins that appear in spring. They are wind-pollinated and self-incompatible, meaning pollen from one tree cannot fertilize the flowers of the same individual tree. This self-incompatibility has direct practical consequences: when growers cultivate hickories from clonal, grafted trees of the same cultivar, those trees cannot pollinate each other. At least two distinct cultivars must be planted together for a crop to set. Seedlings grown directly from nuts carry enough genetic variation to avoid this problem.

  The fruit that results from successful pollination is a globose or oval nut, 2-5 cm long and 1.5-3 cm in diameter. It sits enclosed within a four-valved husk that splits open when the nut matures. The shell inside is thick and bony in most species; in the pecan it is notably thin. Whether hickory nuts count as true botanical nuts is a matter of some technical debate. Carya nuts and walnut family members both develop within an outer husk, and some botanists classify them as drupes or drupaceous nuts, using the specialized term "tryma" for such structures. The Angiosperm Phylogeny Group, however, classifies the fruit simply as a nut.

• 6. Wood Without Equal

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  Hickory wood is hard, stiff, dense, and shock resistant. There are woods stronger than hickory, and woods harder than hickory, but no other commercial wood combines all four properties at once: strength, toughness, hardness, and stiffness together. That combination has driven its use in tool handles, bows, wheel spokes, walking sticks, drumsticks, and wood flooring.

  Baseball bats were once routinely made of hickory, though ash became the preferred choice for that application over time. Hickory is now gaining ground as the wood of choice for Scottish shinty sticks, partly filling the role ash no longer holds as well. Traditional lacrosse sticks were made of hickory until the 1970s, when the sport shifted to plastic heads mounted on metal shafts. Hickory also served extensively in the construction of early aircraft. One physical limitation matters to anyone working with it: because of its grain structure, hickory absorbs moisture more readily than most commercial woods, making it more prone to warping, shrinkage, and swelling when humidity changes.

  Beyond its structural applications, hickory burns with exceptional efficiency. Its density and high energy content make it a preferred fuel for wood-burning stoves and chimineas. In the Southern United States, it is closely associated with barbecue cooking, both because it grows abundantly across the region and because its smoke adds a distinctive flavor to meat. A bark extract from shagbark hickory is also used to produce a syrup comparable to maple syrup, though with a slightly bitter, smoky character.

• 7. A Tree and Its Insects

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  Several moth species depend on hickory as a larval food plant. The luna moth, the brown-tail moth, the regal moth (whose caterpillars carry the name hickory horn-devils), the walnut sphinx, the hickory tussock moth, and a species called the bride all use hickory leaves at some stage of their development. Two Coleophora case-bearer species, C. laticornella and C. ostryae, are also associated with the tree.

  The hickory leaf stem gall phylloxera, Phylloxera caryaecaulis, is a small insect related to aphids with an equally complex life cycle. Eggs hatch in early spring and the insects quickly become enclosed in galls that form around them on hickory stems and leaves. In a healthy tree these galls are generally harmless, though they can cause damage when the tree is already stressed. Squirrels actively break off gall-infected twigs and eat the galls themselves, possibly attracted by their protein content or their fleshy texture, and deformed leaves and twigs fall from the tree as a result of that activity. The pecan gall curculio, Conotrachelus elegans, a true weevil, also feeds on these same phylloxera galls. The banded hickory borer, Knulliana cincta, is an additional insect found specifically on hickory trees, extending the ecological web further.

• 8. Pecans and Nutrition

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  Pecans, Carya illinoinensis, occupy a special position within the genus. They are regarded as the most important nut tree native to North America, and their notably thin shell sets them apart from most of their relatives. Shagbark and shellbark hickory join the pecan in being considered among the finest nut trees by some growers and foragers.

  Dried hickory nuts in general carry a striking nutritional profile. They are 3% water, 18% carbohydrates, and 13% protein. The dominant component is fat at 64%. In a 100-gram reference amount, dried hickory nuts supply 2749 kilojoules of food energy. They are a rich source of several B vitamins and dietary minerals, with manganese standing out at 220% of the daily value per serving. That concentrated energy and nutrient density helps explain why hickory nuts were a staple for Eastern Woodlands peoples across the middle Archaic period and long after, and why the pecan in particular became the only nut tree in North America to achieve wide commercial cultivation.